We intend to continue our efforts to develop polyphosphazene polymers as hydrogels and membranes for use as artificial tissues, semipermeable membranes, matrices for the slow release of drugs, and substrates for the immobilization of enzymes and other biologically-active agents. The work will revolve around the selection of suitable hydrophilic side groups attached to the polymer chain, the development of polymer crosslinking reactions, and the use of these materials to mediate the diffusion of small molecule solutes. Biocompatibility studies are also planned, to be undertaken through a collaborative research arrangement.